Rotary electric machines include windings and supporting hardware that occupy substantial space. However, attempts have been made to reduce the size and simplify the construction of such a device. For example, alternators used in motor vehicles have been axially shortened as a result of a rearrangement of the components making up the device. In one previously known improvement, a slip ring is carried on an end of the rotor shaft, while bearing lands are formed on opposite ends of the rotor carrying land of the alternator shaft. Rearrangement of the slip rings to the shaft end permits the rings to be carried outside of the housing, and substantially reduces the axial length of the housing protecting the windings by reducing the axial distance between the bearings used to support the shaft.
Although the reduced axial dimension provides improved packaging for the alternator, the connection of the conductors on the slip ring with the coil windings on the rotor becomes more difficult because the ring is no longer next to the rotor assembly and the bearing obstructs connection of the rings to the rotor. Accordingly it has been found useful to provide a slot in the shaft through which conductors such as lead wires can be extended from a slip ring to a terminal at the winding on the rotor. Although the slot may be provided by milling the shaft after it is formed, such a separate machining operation is undesirable as it substantially increases the expenses and prolongs the time for manufacturing of the device. For example, a milling operation which cuts the slot must be followed by a finishing step such as a deburring operation to assure that sharp edges do not interfere with further handling or assembly operations.
Nevertheless, assembly operations other than machining would not readily appear to be applicable to construction of the slot in previously known alternator rotor shafts. British Patent No. 116,577 and U.S. Pat. No. 3,842,301 show slots or grooves to carry lead wires to the slip rings. However, the wedge, shaped slot of the British patent and the arcuate groove of Smith's patent are not disclosed as being formed by cold heading.
The prior art also does not disclose cold heading operations for alternator shafts. In a cold heading operation, the grooves formed in a land can extend no deeper than the maximum diameter of the adjacent portion of the shaft without deforming the surface of the adjacent portion. However, in a cold heading operation, the maximum reduction in shaft diameter which can be obtained is quite limited, for example, by the material properties of the blank used to form the shaft. As a result, the limitations on minimum diameter of the adjacent portion of the shaft and the limited depth of the groove in the land of the shaft have been avoided in the alternator shafts of the prior art by relying upon machining, and would be considered undesirable design parameters for cold heading of the shaft. For example, for grooves in bearing lands adjacent a narrow shaft end for receiving the slip ring of an alternator rotor shaft, a machining operation has conventionally been used.
As a result, the previously discussed machining operations are conventionally used to provide slots as conductor grooves for lead wires in an alternator shaft in order to reach the slip rings despite the time, labor and expense necessary to provide such a structure.